The invention relates to a local area network operating in the asynchronous transfer mode (ATM) for transmitting cells, comprising a plurality of network interfaces coupled to a ring by ring connections, each network interface including a switch.
A local area network (LAN) operating in the asynchronous transfer mode is known from EP-0 641 105 A2. This network comprises a plurality of network interfaces which include each a transmit and a receive terminal, and stations coupled to the network interface by wires. Cells containing information about the destination, for example, of a certain station are transmitted by the ring formed in this manner. A network interface comprises a switch and a controller. The switch contains respective path memories which are assigned each to a receive connection. When a cell is received, the switch performs switching or coupling operations instructed by the switch modes based on the stored paths. For example, an incoming cell is transferred to the controller, to the station and/or to the ring. The controller is, for example, charged with connection set-up and disconnection operations.
When an asynchronous transfer mode is used in a system, payload information such as telephone, picture or sound signals are transmitted in fixed-length blocks via digital signal processing arrangements. A cell having a predetermined number of bytes (for example, 53 bytes) is denoted a fixed-length block. Each cell comprises a header field having a length of, for example, 5 bytes, and an information field in which the payload information is accommodated having a length of, for example, 48 bytes. In such a header field are contained address information, data for error detection and data for control indication bytes. Address information comprises a trunk identifier which is referenced VPI (Virtual Path Identifier), and a link identifier which is referenced a VCI (Virtual Channel Identifier). VPI and VCI together denote a virtual link or a virtual channel. A group of a plurality of virtual channels is denoted a virtual path, featured by the trunk identifier.